Process for the decomposition of diolefin monosulphones



Patented July 31, 1945 PROCESS FOR THE DECOMPOSITION 0! mm HONOSULPIIONIB messlr msnmmanemnmies- Phlllipsl'etroleam V le.

0kla.,'alsisnors to company, a corporation of Delaware Application December 1c, 1941, Serum. 423,230 120mm. (01. zoo-sen This invention relates to a process for decomposing aliphatic conjugated diolefln monosulphones for the recovery of the dioleiln contained therein.

Aliphatic coniusated dioleflns, such as butadien isopr p oerylene, and the like, my be separated irom mixture with other hydrocarbons by reacting with sulphur dioxide under conditions such as to prevent reaction oi mono-oleflns with sulphur dioxide and also to prevent formation of polymeric sulphones (p lv ulphonesi of 11811 molecular weisht from the dioleilns. Thus the reaction may be carried out at low temperatures in the presence of inhibitors such as hydroquinone, pyrogallol, phenyl-beta-naphthyiamine and the like. or at relatively high temperatures, say 100' to roof C. in the absence of catalysts or inhibitors. In either case the principal product iormed is the aliphatic coniuiated diolefln monosulphone with minor amounts or. or no. We sulphones and hydrocarbon polymers. The diolenn monosulphone is characterised by its solubility in water and common orsanic solvents, and by the tact that upon heating it is decomposed into its components. The monosulphone may be recovered from other materials in the reaction mixture such as unreacted hydrocarbons and sulphur dioxide by any suitable means such as distillation, extraction,- etc.

The recovered monosulphone may be decomposed by heating to temperatures above about 90' 0., and preferably above about 110 C. However. it the dtion is conducted in accordance with the Prior Practice, as by boiling the materialinapottowhichisattacheda spray trap,

cleaning which requires discontinuance oi operation. involves excessive labor and other charges, and prevents operation in a continuous manner.

The principal object oi the present invention is to provide an improved process for eiiecting decomposition oi aliphatic conjugated dioienn monosulphones. Another obiect to devise a proces in which better control of temperature is readily obtained.

A further obiect is to provide a process to: deoomponng such monosulphones wherein the depositiim oi tarry or other insoluble material in the decomposition zone is substantially or entirely avoided.

Auotherobiectis tominimisethelossoi'diolefin by polymerisation and/or polysulphone formation during the decomposition step.

Another obiect is to provide a process more adapted to continuous operation.

Numerous other obiects will hereinafter ap- Dill.

In the accompanying drawing: Figs. 1 to 3 show diasrammatically terms of apparatus which maybeusedincarryingoutthepresentinvention. rm. 1 showing equipment particularly adaptediorcarryingouttheprocesswhsreinthe extent or monosulphone decomposition per pass throush the tion acne is limited, and Figs. 2 and 8 showing equipment ior use in carryins out a modified ion-mot the proces wherein acarrleris used.

In accordance withthe present invention the preferably essentially pure. is destricted cross-section, such as a tube, preferably intbeiormoiacoihasatubestlllor pipestili heaterottheradianttypain whichitisbrought and maintained at a temperature mmciently elevated andtor a period or time suiliciently proto elect decomposition of a substantial roportion oi the monosulphone. The decommixturs is continuously removed irom oithereactionloneataratesuiiie elenttomsintainconstantpressureinthsreacand preferably as near atmospherleas or by the presence ot'an inert diluent steam. men-tree due gas. methane, ethane, propane or other or the reactionsonaorbyrapidcoolingoltbe oideeomposidentoapointbelowthatatwhich re-reacticn or diolefln misht,

tionsone. Preierablythereaciionaoneismaintalmdatsubstantiallyatmosphericpressmeas by allowing tree flowing-out oi the reaction mixtureastormedasitraachestheexitend, thattheonlypressureisthatduetotheresistencetoflowinthetubc.

We have round that by continumislr passins themonesulphonethrouchareactiontubsinthe i resoins manner under such that anytarrymaterieiiormediscarriedalohswith the reaction product and deposited outside the reaction tube that wntinuous operation is made possible without the inconvenience and expense at frequent stopme and cleaning or the reactionsone.

We have further found that deposition or tarry andotherproductsmaybestillmereeilectively avoided by either or both of two procedures as follows:

(1) By adjusting the oontacttime and temperaturesothat thesulphenelsnotoompletelydeinonemiihmhth w tarryorothermaterialiromthereactiontubeto a polauat ouiside where itcanbeconveniently separa (zlllyprovidlngacarrierwhichispessed throuah the decomposition lone with the guiphone. Thecarriershouldbeollewhlchhliquid at ordinary or moderately elevated temperaturessothatitmaybeemuisiiledwithtbeliquid monosulphone. It should be liquid well belowthedecompositiontemperaturemsintainedin actionproductsinauysuitablemannerandrecible, to iorm an intimate aqueous emulsion for introduction to the decomposition tube.

The monosulphone. with or without a diluent and/or liquid carrier, is introduced to the reaction tube under sumcient pressure to overcome the resistance thereof. The reaction tube is maintained throughout at a substantially constant temperature: say between about 100' C. and about 400 C. and preferably between about 150 C. and about 250' q.,;in any suitable manner as as by liquid or nuid-iacketing, electrical Jacketing, or immersion in a suitable heatinc medium suchasabodyoi'liquidorgasatthedesiredtemperature or at the iransition temperature, or by useolasuitableheatingiumaceorsoneinwhich the reaction tubeandahouldremainintheliqmd 88 tuelisburnedorsteaminlectsd.

iormatthetemperaturesandmederatepressuresencounteredinthetionsone. It

peratures encountered. It should be inert with respecttothematerialswithwhichitcomesinto flisdeairab i ficontact. It is preferably substantially immiscible with and a now-solvent for the'liquid monmulsolvent for the dioleiln formed but is Preferably a non-solvent tor sulphur dioxide. A blah-boilingmineraloilsuchaszas oil,mineralssaloil, andthelikehprei'erred. liis'ampleaoiothersuitable carriers are beta, beta-dichlordlethyletber, diphenyl. diphuiyl oxide, etc. Suitable pal-amnic. aromatic. or naphtbenic liquids may also be When using either of the ioreeoing procedures,

The time oi" through the reaction tube is preferably such that at least about 30% o! the incomingwhere rooeduret )aboveis'usedtbeupperlimit The time oi maintenance at the decomposition temperature will vary inversely with the temperature of decomposition. 'Ihus it may vary from about 400 minutes at iililCJoaboutaseoondorlessatilfiiHlMf C.

The decomposition products are continuously removed at substantially atmospheric pressure from the reaction some and treated in any suitable manner to separate undeoomposed sulphone and tarry or similar materials from the lessons decomposition products and gaseous diluent, and. ii desired irom the carrier liquid. The monosulwith a paraillnic liquid absorbing medium whichha's aboillns-point sumcientiy above that oi the dloledn to enable separation thereirom by ordinaryiraetienatiomwhichisagoodsolmtior the dioleiln. and substantially a nonsolvent for thecopendineapplicationoioneoiuaserialito 428,585, flied Dec. 18, 1041.

Whereadilumtgasispresentitgoesalimg with and dilutes the sulphur dioxide recovered.

isdeoomposedperpass.

Where the same liquid medium is used as the carrier and as the diolefin extraction medium, such as gas oil, mineral seal oil, etc., separation of the carrier from the reaction mixture before entering the extraction zone is optional. In case separation of carriers is dispensed with, a portion of the stripped, absorption medium may be recycled to act as carrier. uids are used for the functions of carrier and absorption medium, separation of the carrier before entering the extraction zone is usually essential. In either event, stripping of the decomposition products from the carrier may be practiced and the stripped carrier liquid recycled, thus being kept entirely separate from the diolefln absorption medium. Usually the thus recycled carrier liquid will be in admixture with any undecomposed monosulphone.

In the reaction tube the flow may be either streamline or turbulent, preferably the latter because of more rapid reaction and less side reactions. The adjustment of the necessary factors to give either streamline or turbulent flow is well within the skill of the art. Preferably the reaction tube is free from any restrictions whatever, such as packing, catalyst, bailies, etc.

Referring to Fig. 1, the monosulphone is introduced to the system via pipe i. If desired, a diluent such as steam, methane, ethane, oxygenfree flue gas, or the like, may be introduced through pipe 2. The sulphone, in liquid form, with or without the diluent gas, passes through the heated reaction zone 3 which takes the form of a tubular coil surrounded by any suitable heating means 3A for maintaining the desired temperature. The temperature maintained in the reaction zone may be in the range oi from about 100 to about 400 C., and preferably in the range of from about 150 to about 250 C. The heating time is adjusted so that at least about 30% but not more than about 90% of the sulfone is decomposed in passing through the heating zone 3. The exact value of the heating time varies widely with the temperature maintained in the decomposition zone, varying inversely therewith, and varying to a lesser extent with the particular sulphone being decomposed. Thus piperylene monosulphone decomposes at a somewhat faster rate than the sulphones of butadiene or isoprene at the same temperature. The duration of the heating may range from as long as 400 minutes at 100 C. to a second or less at 250 to 300 c.

From reaction zone 3, the jreaction mixture passes to heat exchanger 4 where the temperature of the mixture is so adjusted that the undecomposed sulphone, containing only limited amounts of dissolved sulphur dioxide and diolefln or other volatile hydrocarbons, separates as a. liquid phase in separator 5. This sulphone is withdrawn from separator 5 via pipe 3 andpasses to the cleaning and purifying zone H, where it is freed of undesired products such as tarry material, polysulphone or the like in any manner, as for example, by allowing insoluble materials to settle out, or through the use of selective solvents. Dissolved sulphur dioxide and similarly readily volatile material may be removed by distillation ii desired. The lines ill'and II are indicated for conveying gaseous and solid impurities, respec-- tively, from the unit l2. Polysulphone of either of the aliphatic conjugated diolefln or of cyclopentadlene are quite heat-stable and may be separated out in solid form in unit I! by suitable precipitation procedure. The pure undecom- Where diflerent liqposed monosulphone is then recycled via lin I! to the stream of fresh monosulphone entering the decomposition tube 3.

If desired, unit I! may be by-passed partially or entirely by line 9. In some cases the undecomposed monosulphone phase recovered from unit 5 may be so pure that use of unit l2 may be dispensed with entirely.

The uncondensed products from unit 5, comprising mainly diolefin and sulphur dioxide together with diluent gas it used, pass via line 6 to cooler I in which. they may be rapidly cooled to well below the temperature at which reaction therebetween might occur, and then pass to separator is where water containing dissolved sulphur dioxide separates if steam was used as the diluent in the decomposition step. Small amounts of tarry material or polymer (polysulphone or polymerized diolefln) not removed in 5 may also separate in unit Ii. The condensate is withdrawn from is via line H.

The uncondensed products from unit i5, which consist essentially of diolefin, sulphur dioxide and diluent if a non-condensible diluent was used in mi the decomposition step, leave via line l8 and ma be separated into the several components in any desired manner as by fractionation, absorption and the like. We have shown an absorption step, employing a mineral oil, as for example gas oil, mineral seal oil. or the like.

The uncondensed products next are compressed by compressor It and then pass to absorber i! into the top of which absorbent oil is introduced via line 26. Heat may be supplied at the bottom of the absorber by means of the reboiler coil 2|. The unabsorbed products (sulphur dioxide and diluent gas if used) leave via line 20. The enriched oil, containing dissolved diolefln, passes via line 22 to the top of stripping tower 23 Heat is applied to the bottom of tower 23 by reboiler coil 25. Steam may be introduced through line. to aid in the stripping if desired.

The diolefln product passes through line 24 and cooler 20 to storage or further purification steps if desired, The stripped oil is withdrawn via line 26 and after cooling in cooler 21 passes to the top of absorber l9. Oil may be withdrawn via line ill for cleaning if desired.

In Fig. 2. the sulphone enters via line I. Makeup oil carrier, such as gas oil, enters via line 3| combining with gas oil recycled from the oil absorption step via line 32. The gas oil and sulphone are combined and pass, together with any recycled sulphone from line I: through pump 33 where the streams are thoroughly mixed. Thorough intermixture at this point is essential in order to insure intimate contact and formation of an emulsion which will last at least until the reaction zone is reached, since the gas oil carrier and the liquid monosulphone are immiscible. Diluent, if desired, enters the line I after mixer ll via line 2. The combined streams then pass through reaction tube i where temperature and heating time are regulated to eil'ect partial or complete decomposition of the sulphone per pass through the heating zone I. The reaction eifluent is cooled in exchanger I, to a point well below the temperature at which re-actlon would occur, and passes to pump 4A where the pressure is raised to a value suitable for the oil absorption step. as for example to from about 20 to about pounds per square inch gauge. The products then pass to separator I where an undecomposed sulphone and insoluble products are separated out. This material may be removed via line 34 or recycled via line l3 with or without partial or complete purification in unit H as before. The mixture of gas oil, dlolefln and sulphur dioxide passes via line [8 to an oil absorption step as described for Fig. l. The carrier (gas oil) may be removed before entry into the oil absorption step, stripped of dissolved diolefin. and recycled. Alternatively, where the same oil, for example gas oil, is used as a carrier and as an absorption oil, the excess stripped oil accumulating in the exhaustion or stripping step in the oil absorption end of the process may be recycled to the incoming feed to mixing pump 33 via line 32. If desired, a portion of the gas oil may be removed from the system for cleaning via line 30. as before.

Figure 3 shows a process wherein a carrier, e. g.. gas oil, is employed, the carrier oil being kept separate from that used in the product separation step when this is done by means of oil absorption. The sulphone enters the system through pipe I, make-up gas oil enters through pipe 3|, and combines with recycled gas oil and any recycled sulphone flowing through pipe 35; The combined gas oil and sulphone are thoroughly mixed by means of pump 33. Diluent. if desired. is added through pipe 2, and the combined streams passto the decomposition zone 3, where temperature and heating time are regulated to effect either partial or complete decomposition of the sulphone. The products from the decomposition zone are cooled in the cooler 4 and passed to stripping column 36, where the gas oil is freed of diolefins and sulphur dioxide. Heat is supplied to the bottom of this stripper by means of reboiler coil 31. The stripped gas oil and any undecomposed sulphone pass from the bottom of 86 through pipe 38. Any desired portion may be passed through pipe 39 to purincation means not shown in the drawing to be cleaned prior to returning to the process. The remaining product may be recycled directly to the conversion.zone 3 by means of line 35. The stripping may be aided in some cases by returning to 35 through pipe 43 some sulphur dioxide or other gaseous product separated at a later stage of the process. The stripped products pass through pipe 40, cooler 4|, compressor 42 to separating means 44, where the diolefins are separated from sulphur dioxide and diluent, if this was used. Separating means 44 may be any suitable process, as for example, oil absorption, distillation and the like. Sulphur dioxide, and diluent if used, leave separation zone 44 via line 20 from which any desired portion may berecycled to the column 36 via line 43. The pure diolefin is removed via line 24.

If desired. purification means l2 similar to that shown in line 13 for Figs. 1 -nd 2 may be interposed in line 35 for purifying recycled gas oil and monosulphone. to separate tarry materials or the like before recycling thereof.

It will be understood that our invention is ca: pable of numerous modifications without departing from the spirit thereof, that the foregoing description is for illustrative purposes only to teachthose skilled in the art how to practice our invention. and that our invention is to be limited only by the language of the appended claims.

As used herein, the term of restricted cross section" means of limited cross-section, that is of cross-sectional area such that flow is confined to substantially one general direr ion from one end thereof to the other. Generally the tube used will have an internal diameter not exceeding about 4 inches and not smaller than about one-sixteenth of an inch. Usually tubes of a size such as is commonly used for hydrocarbon crac'king operations will be employed.

We claim:

1. The process of decomposing monosulphone of aliphatic conjugated diolefin which comprises continuously feeding said monosulphone into the inlet end of a closed elongated zone of restricted cross section such that flow is confined to one general direction from the inlet to the outlet end thereof. continuously passing said monosulphone through said zone from the inlet to the outlet end thereof while subjecting it to a temperature sufficiently elevated and to other conditions such as to effect incomplete decomposition of said monosulphone to the diolefin and sulphur dioxide, and continuously removing the decomposition mixture from the outlet end of said zone.

2. The process of decomposing monosulphone of aliphatic conjugated diolefln which comprises continuously feeding a mixture of said monosulphone and an inert stable liquid carrier which remains liquid and undecomposed during the decompositiop into the inlet end of a closed elongated zone of r stricted cross section such that flow is confined 0 one general direction from the inlet to the outlet end thereof, continuously passing said mixture through said zone from th inlet to the outlet end thereof while subjectin it to a temperature suflflciently elevated and to other conditions such as to effect decomposition of said monosulphone to the dioleiln and sulphur dioxide. and continuously removing the decomposition mixture from the outlet end of said zone.

3. The process of decomposing monosulphone of aliphatic conjugated diolefin which comprises feeding a mixture of said monosulphone and gas oil as a carrier into the inlet end of a closed elongated zone of restricted cross section such that flow is confined to one general direction from the inlet to the outlet end thereof, continuously passing said mixture through said zone from the inlet to the outlet end thereof while subjecting it to a temperature sufficiently elevated and to other conditions such as to effect decomposition of said monosulphone to the diolefin and sulphur diox de. and continuously removing the decomposition mixture from the outlet end of said zone.

4. The process of decomposing monosulphone of aliphatic conjugated diolefin which comprises continuously feeding an emulsion of the liquid monosulphone and an immiscible, inert, stare carrier which remains liquid and undecomposed during the decomposition into the inlet end or a closed elongated zone of restricted cross section such that flow is confined to one general direction from the inlet to the outlet end thereof, continuously passing said emulsion through said zone from the inlet to the outlet end thereof while subjecting it to a temperature sufficiently elevated and to other conditions such as to effect decomposition of said monosulphone to the dioleiln and sulphur dioxide, and continuously removing the decomposition mixture from the outlet end of said zone.

5. The process of decomposing monosuiphone of aliphatic conjugated diolefin which comprises continuously feeding an emulsion of an aqueous solution of said monosulphone and a water-immiscible, inert, stable liquid carrier which remains liquid and undecomposed during the decomposition into the inlet end of a closed elongated zone of restricted cross section such that flow is confined to one general direction from the inlet to the outlet end thereof, continuously passing said emulsion through said zone from the inlet to the outlet end thereof while subjecting it to a temperature suiliciently elevated and to other conditions such as to eflect decomposition of said monosulphone to the dioleiln and sulphur dioxide, and continuously removing the decomposed mixture to the outlet end or said zone.

6. The process of decomposing monosulphone of aliphatic conjugated diolefin which comprises continuously feeding a mixture of said monosulphone and a liquid carrier which remains liquid and undecomposed during the decomposition into the inlet end of a closed elongated zone of restricted cross section such that flow is confined to one general direction from the inlet to the outlet end thereof; continuously passing said mixture through said zone from the inlet to the outlet end thereof while subjecting it to a temperature sufllciently elevated and to other condi tions such as to effect decomposition of said monosulphone to the diolefin and sulphur dioxide, and continuously removing the decomposition mixture from the outlet end of said zone.

I. The process or claim 6 wherein said temperature is from 100" 0.1 400 c.

8. The process oi claim 6 wherein said teml firature is from 150 C. to 250 C.

9. The continuous process or eilecting thermal decomposition of aliphatic conjugated diolefin zone up to and it at a temperature between about 150' C. and about 250 C. for a sufiicient period of time to eflfect at least about 30% decomposition of the incoming monosulphone in a single pass through the zone, continuously supplying said liquid monosulphone to the entrance end or said zone under pressure only sumcient to force the reaction stream through said zone, continuously maintaining the material at exit end of said zone at substantially atmospheric pressure, continuously removing the decomposition mixture from the exit end of said zone at a rate sufficient to maintain substantially constant pressure in said zone, whereby any tarry and like material formed in said zone is continuously carried along with the reaction stream to a point outside said zone so that continuous operation is possible.

10. The process of claim 9 including the further step of adjusting reaction time and temperature in such manner that the monosulphone is not more than about decomposed in a single pass whereby the undecomposed monosulphone continuously carries tarry and like material irom the reaction tube to a point outside said zone.

11. The process of claim 9, said carrier being liquid at temperatures well below the reaction temperatures and remaining liquid at the reaction temperatures, said carrier being stable and inert, being substantially a non-solvent for the monosulphone, a solvent for tarry and like material, a solvent for the diolefln formed and substantially a non-solvent for sulphur dioxide, whereby said carrier continuously carries tarry and like material from said zone to a point outside said zone.

12. The process of claim 9 wherein said carrier is gas oil.

FREDERICK E. FREY. HAROLD J. HEPP. 

